This is a milestone release, for use at your own risk. Significant development changes take place in milestone releases and you may encounter compatibility issues, such as data format changes that require attention in addition to the usual procedure of running mysql_upgrade. For example, you may find it necessary to dump your data with mysqldump before the upgrade and reload it afterward.
Beginning with MySQL 5.6.5, Oracle no longer provides binaries for Mac OS X 10.5. This aligns with Apple no longer providing updates or support for this platform.
Data Type Notes
Previously, at most one
column per table could be automatically initialized or updated
to the current date and time. This restriction has been lifted.
TIMESTAMP column definition
can have any combination of
CURRENT_TIMESTAMP clauses. In addition, these clauses
now can be used with
column definitions. For more information, see
Automatic Initialization and Updating for TIMESTAMP and DATETIME.
Replication with GTIDs
Important Change; Replication:
This release introduces global transaction
identifiers (GTIDs) for MySQL Replication. A GTID is
a unique identifier that is assigned to each transaction as it
is committed; this identifier is unique on the MySQL Server
where the transaction originated, as well as across all MySQL
Servers in a given replication setup. Because GTID-based
replication depends on tracking transactions, it cannot be
employed with tables that employ a nontransactional storage
engine such as
MyISAM; thus, it is
currently supported only with
Because each transaction is uniquely identified, it is not
necessary when using GTIDs to specify positions in the
master's binary log when starting a new slave or failing
over to a new master. This is reflected in the addition of a new
MASTER_AUTO_POSITION option for the
CHANGE MASTER TO statement which
takes the place of the
MASTER_LOG_POS options when executing this
statement to prepare a MySQL Server to act as a replication
To enable GTIDs on a MySQL Server, the server must be started
with the options
options are needed whether the server acts as a replication
master or as a replication slave; the
--disable-gtid-unsafe-statements options are
new in this release. Once the master and slave have each been
started with these options, it is necessary only to issue a
CHANGE MASTER TO ... MASTER_AUTO_POSITION=1
START SLAVE on the
slave to start replication.
A number of new server system variables have also been added for monitoring GTID usage. For more information about these options and variables, see Global Transaction ID Options and Variables.
As part of these changes, three new
added for reading binary logs produced when the server
participates in replication with GTIDs.
Due to an issue discovered just prior to release, you cannot
import a dump made using mysqldump from a
MySQL 5.5 server to a MySQL 5.6.5 server and then use
mysqlupgrade on the MySQL 5.6.5 server
while GTIDs are enabled; doing so makes it impossible to
connect to the server normally following the upgrade. Instead,
you should import the dump and run
mysqlupgrade while the MySQL 5.6.5 server
is running with
--gtid-mode=OFF, then restart
--gtid-mode=ON. (Bug #13833710)
(mysqlupgrade can be executed when the
server is running with
--gtid-mode set either to
OFF, or to
For additional information about GTIDs and setting up GTID-based replication, see Replication with Global Transaction Identifiers.
Host Cache Notes
MySQL now provides more information about the causes of errors that occur when clients connect to the server, as well as improved access to the host cache, which contains client IP address and host name information and is used to avoid DNS lookups. These changes have been implemented:
status variables provide information about connection errors
that do not apply to specific client IP addresses.
The host cache has additional counters to track errors that do apply to specific IP addresses.
Schema table exposes the contents of the host cache so that
it can be examined using
SELECT statements. Access to
host cache contents makes it possible to answer questions
such as how many hosts are cached, what kinds of connection
errors are occurring for which hosts, or how close host
error counts are to reaching the
variable limit. The Performance Schema must be enabled or
this table is empty.
If you upgrade to this release of MySQL from an earlier
version, you must run mysql_upgrade (and
restart the server) to incorporate this change into the
The host cache size now is configurable using the
variable. Setting the size to 0 disables the host cache.This
is similar to disabling the cache by starting the server
more flexible because it can also be used to resize, enable,
or disable the host cache at runtime, not just at server
startup. If you start the server with
--skip-host-cache, the host
cache cannot be re-enabled at runtime.
For more information, see DNS Lookup Optimization and the Host Cache, and The host_cache Table. (Bug #22821, Bug #24906, Bug #45817, Bug #59404, Bug #11746048, Bug #11746269, Bug #11754244, Bug #11766316)
These query optimizer improvements were implemented:
EXPLAIN statement now can
produce output in JSON format. To select this, use
EXPLAIN FORMAT =
FORMAT = JSON, the output
information, as well as extended and partition information.
has also changed so that empty columns contain
NULL rather the empty string. In
UNION RESULT rows have
Using filesort in the
Extra column because a temporary table is
used to buffer
To work for both Optimizer Trace and JSON-format
EXPLAIN output, the
end_marker parameter for the
variable has been moved to a separate
variable. This is an incompatible change to the
For more information, see
Internals: Tracing the Optimizer.
The optimizer tries to find the best query execution plan by beginning with the most promising table and recursively adding to the plan the most promising of the remaining tables. Partial execution plans with a higher cost than an already found plan are pruned. The optimizer now attempts to improve the order in which it adds tables to the plan, resulting in a reduction of the number of partial plans considered.
A new status variable,
counts the number of iterations the optimizer makes in
execution plan construction for the previous query.
The optimizer uses semi-join and materialization strategies to optimize subquery execution. See Optimizing Subqueries with Semi-Join Transformations, and Optimizing Subqueries with Subquery Materialization. In addition, the Batched Key Access (BKA) Join and Block Nested-Loop (BNL) Join algorithms used for inner join and outer join operations have been extended to support semi-join operations. For more information, see Block Nested-Loop and Batched Key Access Joins.
Several flags have been added to the
variable to enable control over semi-join and subquery
materialization strategies. The
flag controls whether semi-joins are used. If it is set to
loosescan flags enable finer control over
the permitted semi-join strategies. The
materialization flag controls whether
subquery materialization is used. If
materialization are both
on, semi-joins also use materialization
where applicable. These flags are
default. See Controlling Switchable Optimizations.
For expressions such as
a column to a list of values, the optimizer previously made
row estimates using index dives for each value in the list.
This becomes inefficient as the number of values becomes
large. The optimizer now can make row estimates for such
expressions using index statistics instead, which is less
accurate but quicker for a large number of values. The point
at which the optimizer switches from index dives to index
statistics is configurable using the new
system variable. For more information, see
Equality Range Optimization of Many-Valued Comparisons.
Performance Schema Notes
The Performance Schema has these additions:
The Performance Schema now maintains statement digest information. This normalizes and groups statements with the same “signature” and permits questions to be answered about the types of statements the server is executing and how often they occur.
statement_digest consumer in the
controls whether the Performance Schema maintains digest
The statement event tables
DIGEST_TEXT columns that contain
digest MD5 values and the corresponding normalized
statement text strings.
table provides aggregated statement digest information.
If you upgrade to this release of MySQL from an earlier version,
you must run mysql_upgrade (and restart the
server) to incorporate these changes into the
Passwords stored in the older hash format used before MySQL 4.1
are less secure than passwords that use the native password
hashing method and should be avoided. Pre-4.1 passwords and the
mysql_old_password authentication plugin are
now deprecated. To prevent connections using accounts that have
pre-4.1 password hashes, the
secure_auth system variable is
now enabled by default. (To permit connections for accounts that
have such password hashes, start the server with
MySQL client programs now issue a warning if a password is given on the command line that this can be insecure.
Functionality Added or Changed
OPTION modifier for the
SET statement has been
--ignore-builtin-innodb is now
ignored if used.
MySQL-shared-compat RPM package enables
users of Red Hat-provided
packages to migrate to Oracle-provided
MySQL-shared-compat now replaces the Red Hat
mysql-libs package by replacing
libmysqlclient.so files of the latter
package, thus satisfying dependencies of other packages on
mysql-libs. This change affects only users of
Red Hat (or Red Hat-compatible) RPM packages. Nothing is
different for users of Oracle RPM packages.
As of MySQL 5.5.3, the
LOCK TABLES ...
LOW_PRIORITY WRITE has no effect. This modifier is now
deprecated. Its use should be avoided and now produces a
TABLES ... WRITE instead.
A new CMake option,
MYSQL_PROJECT_NAME, can be set on
Windows or Mac OS X to be used in the project name.
system variable is enabled, slow queries that do not use indexes
are written to the slow query log. In this case, it is now
possible to put a logging rate limit on these queries by setting
system variable, so that the slow query log does not grow too
quickly. By default, this variable is 0, which means there is no
limit. Positive values impose a per-minute limit on logging of
queries that do not use indexes. The first such query opens a
60-second window within which the server logs queries up to the
given limit, then suppresses additional queries. If there are
suppressed queries when the window ends, the server logs a
summary that indicates how many there were and the aggregate
time spent in them. The next 60-second window begins when the
server logs the next query that does not use indexes.
(Bug #55323, Bug #11762697)
Several subquery performance issues were resolved through the implementation of semi-join subquery optimization strategies. See Optimizing Subqueries with Semi-Join Transformations. (Bug #47914, Bug #11756048, Bug #58660, Bug #11765671, Bug #10815, Bug #11745162, Bug #9021, Bug #13519134, Bug #48763, Bug #11756798, Bug #25130, Bug #11746289)
The mysql client now supports an
option. The option value is an SQL statement to execute after
connecting to the server. If auto-reconnect is enabled, the
statement is executed again after reconnection occurs.
(Bug #45634, Bug #11754087)
A new server option,
the Windows service control manager's service start timeout. The
value is the maximum number of milliseconds that the service
control manager waits before trying to kill the MySQL service
during startup. The default value is 15000 (15 seconds). If the
MySQL service takes too long to start, you may need to increase
this value. A value of 0 means there is no timeout.
(Bug #45546, Bug #11754011)
ucs2_general_mysql500_ci collations have been
added that preserve the behavior of
ucs2_general_ci from versions of MySQL
previous to 5.1.24. Bug #27877 corrected an error in the
original collations but introduced an incompatibility for
columns that contain German
'ß' LATIN SMALL
LETTER SHARP S. (As a result of the fix, that character compares
equal to characters with which it previously compared
different.) A symptom of the problem after upgrading to MySQL
5.1.24 or newer from a version older than 5.1.24 is that
CHECK TABLE produces this error:
Table upgrade required. Please do "REPAIR TABLE `t`" or dump/reload to fix it!
REPAIR TABLE could
not fix the problem. The new collations permit older tables
created before MySQL 5.1.24 to be upgraded to current versions
To convert an affected table after a binary upgrade that leaves
the table files in place, alter the table to use the new
collation. Suppose that the table
one or more problematic
utf8 columns. To
convert the table at the table level, use a statement like this:
ALTER TABLE t1 CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_mysql500_ci;
To apply the change on a column-specific basis, use a statement
like this (be sure to repeat the column definition as originally
specified except for the
ALTER TABLE t1 MODIFY c1 CHAR(N) CHARACTER SET utf8 COLLATE utf8_general_mysql500_ci;
To upgrade the table using a dump and reload procedure, dump the
table using mysqldump, modify the
CREATE TABLE statement in the
dump file to use the new collation, and reload the table.
After making the appropriate changes,
TABLE should report no error.
For more information, see Checking Whether Tables or Indexes Must Be Rebuilt, and Rebuilding or Repairing Tables or Indexes. (Bug #43593, Bug #11752408)
MySQL distributions no longer include the GPL
readline input-editing library. This results
in simpler maintenance and support, and simplifies licensing
SET TRANSACTION and
START TRANSACTION statements
READ WRITE and
ONLY modifiers to set the transaction access mode for
tables used in transactions. The default mode is read/write,
which is the same mode as previously. Read/write mode now may be
specified explicitly with the
READ ONLY prohibits table
changes and may enable storage engines to make performance
improvements that are possible when changes are not permitted.
The optimizer now takes into account
page sizes other than 16KB, which can be configured with the
innodb_page_size option when
creating a MySQL instance. This change improves the estimates of
I/O costs for queries on systems with non-default
InnoDB page sizes.
Memory allocation for
InnoDB tables was
reorganized to reduce the memory overhead for large numbers of
tables or partitions, avoiding situations where the
“resident set size” could grow regardless of
FLUSH TABLES statements. The problem was most
evident for tables with large row size. Some of the memory that
was formerly allocated for every open table is now allocated
only when the table is modified for the first time.
(Bug #11764622, Bug #57480)
Incompatible Change; Replication:
CHANGE MASTER TO statements were
written into the error log using quoted numeric values, although
the syntax for this statement does not allow such option values
to be quoted. This meant that such statements could not be
copied from the error log and re-run verbatim. Now
CHANGE MASTER TO statements are
written to the error log without the extraneous quotation marks,
and so are syntactically correct as logged.
A change in MySQL 5.6.3 caused
LAST_DAY() to be more strict and
reject incomplete dates with a day part of zero. For this
function, a nonzero day part is not necessary, so the change has
Important Change; InnoDB:
When a row grew in size due to an
operation, other (non-updated) columns could be moved to
off-page storage so that information about the row still fit
within the constraints of the
size. The pointer to the new allocated off-page data was not set
up until the pages were allocated and written, potentially
leading to lost data if the system crashed while the column was
being moved out of the page. The problem was more common with
ROW_FORMAT=COMPRESSED along with the
Barracuda file format, particularly with the
enabled, because page allocation operations are more common as
.ibd tablespace files are extended.
Still, the problem could occur with any combination of InnoDB
version, file format, and row format.
A related issue was that during such an
UPDATE operation, or an
INSERT operation that reused a delete-marked
record, other transactions could see invalid data for the
affected column, regardless of isolation level.
The fix corrects the order of operations for moving the column data off the original page and replacing it with a pointer. Now if a crash occurs at the precise moment when the column data is being transferred, the transfer will not be re-run during crash recovery.
In MySQL 5.1, this fix applies to the InnoDB Plugin, but not the built-in InnoDB storage engine. (Bug #13721257, Bug #12612184, Bug #12704861)
Important Change; Partitioning: The query cache did not always function correctly with partitioned tables in a transactional context. For this reason, the query cache is now disabled for any queries using partitioned tables, and such queries can no longer be cached. For more information, see Restrictions and Limitations on Partitioning. (Bug #11761296, Bug #53775)
Important Change; Replication:
CHANGE MASTER TO statement
was not checked for invalid characters in values for options
MASTER_USER. In addition, when the server was
restarted, a value containing certain characters was trimmed,
causing the loss of its original value. Now such values are
validated, and in cases where the value contains invalid
characters, including linefeed (
0x0A) characters, the statement fails with an
(Bug #11758581, Bug #50801)
Important Change; Replication:
Moving the binary log file, relay log file, or both files to a
new location, then restarting the server with a new value for
--relay-log, or both, caused the
server to abort on start. This was because the entries in the
index file overrode the new location. In addition, paths were
calculated relative to datadir (rather than to the
The fix for this problem means that, when the server reads an
entry from the index file, it now checks whether the entry
contains a relative path. If it does, the relative part of the
path is replaced with the absolute path set using the
--relay-log option. An absolute
path remains unchanged; in such a case, the index must be edited
manually to enable the new path or paths to be used.
(Bug #11745230, Bug #12133)
An erroneous assertion could occur, in debug builds only, when
creating an index on a column containing zero-length values
A DDL operation such as
ALTER TABLE ... ADD
COLUMN could stall, eventually timing out with an
Error 1005: Can't create table message
(Bug #13636122, Bug #62100, Bug #63553)
If InnoDB was started with
innodb_force_recovery set to a value of 3 or
4, and there are
roll back, normal
shutdown would hang waiting
for those transactions to complete. Now the shutdown happens
immediately, without rolling back any transactions, because
non-zero values for
only appropriate for troubleshooting and diagnostic purposes.
The MySQL server could hang in some cases if the configuration
was turned off.
A Valgrind error was fixed in the function
The configuration option
was renamed to
consistency. This work area is used while creating an
The server could crash when creating an
InnoDB temporary table under Linux, if the
$TMPDIR setting points to a
tmpfs filesystem and
enabled, as it is by default in MySQL 5.5.4 and higher. The
entry in the error log looked like:
101123 2:10:59 InnoDB: Operating system error number 22 in a file operation. InnoDB: Error number 22 means 'Invalid argument'.
The crash occurred because asynchronous I/O is not supported on
tmpfs in some Linux kernel versions. The workaround was to turn
innodb_use_native_aio setting or use
a different temporary directory. The fix causes
InnoDB to turn off the
innodb_use_native_aio setting automatically
if it detects that the temporary file directory does not support
(Bug #13593888, Bug #11765450, Bug #58421)
During startup, the status variable
could be empty for a brief time before being initialized to the
Valgrind errors when referencing the internal function
buf_LRU_scan_and_free_block() were fixed.
InnoDB: The MySQL error log could contain messages like:
InnoDB: Ignoring strange row from mysql.innodb_index_stats WHERE ...
The fix makes the contents of the
innodb_table_stats tables case-sensitive, to
properly distinguish the statistics for tables whose names
differ only in letter case. Other cases were fixed where the
wrong name could be selected for an index while retrieving
References to C preprocessor symbols and macros
UNIV_SET_MEM_TO_ZERO were removed from the
InnoDB source code. They were only used in
debug builds instrumented for Valgrind. They are replaced by
calls to the
InnoDB: The MySQL server could halt with an assertion error:
InnoDB: Failing assertion: page_get_n_recs(page) > 1
Subsequent restarts could fail with the same error. The error
occurred during a purge
operation involving the
change buffer. The
workaround was to set the configuration option
(Bug #13413535, Bug #61104)
A discrepancy could arise between the number of available
logs and the number of undo logs that were currently
active. Now the
variable reports the number of active undo logs, and the new
status variable reports the total number of undo logs.
When doing a live downgrade from MySQL 5.6.4 or later, with
innodb_page_size set to a value other than
16384, now the earlier MySQL version reports that the page size
is incompatible with the older version, rather than crashing or
displaying a “corruption” error.
CREATE TABLE statements
could fail for
InnoDB child tables containing
foreign key definitions. This problem affected Windows systems
only, with the setting
lower_case_table_names=0. It was a regression
from MySQL bug #55222.
(Bug #13083023, Bug #60229)
If the server crashed during a
statement for an
InnoDB table, or a
DROP DATABASE statement for a
InnoDB tables, an index
could be corrupted, causing an error message when accessing the
table after restart:
InnoDB: Error: trying to load index
table_nameInnoDB: but the index tree has been freed!
In MySQL 5.1, this fix applies to the InnoDB Plugin, but not the built-in InnoDB storage engine. (Bug #12861864, Bug #11766019)
A DDL operation for an
InnoDB table could
cause a busy MySQL server to halt with an assertion error:
InnoDB: Failing assertion: trx->error_state == DB_SUCCESS
The error occurred if the DDL operation was run while all 1023
undo slots were in use by concurrent transactions. This error
was less likely to occur in MySQL 5.5 and 5.6, because raising
the number of
InnoDB undo slots increased the
number of simultaneous transactions (corresponding to the number
of undo slots) from 1K to 128K.
(Bug #12739098, Bug #62401)
InnoDB persistent statistics gave less
accurate estimates for date columns than for columns of other
data types. The fix changes the way cardinality is estimated for
nonunique keys, and avoids situations where identical values
could be counted twice if they occurred on different index
variable controls how to delay DML operations when purge
operations are lagging. Previously, if an old consistent read
view was detected, DML operations would not be delayed even
though the purge lag exceeded the
Additionally, if the
was used, situations could arise in which the DML delay time
would continue to increase but not be applied right away due to
the presence an old consistent read view. This could result in a
lengthy DML delay when the accumulated DML delay time is
This fix caps the DML delay at a maximum value, removes the consistent read check, and revises the DML delay calculation. (Bug #12407434, Bug #60776)
With 1024 concurrent
running concurrently and the
CREATE TABLE operation
InnoDB table could fail. The
.ibd file from the failed
TABLE was left behind, preventing the table from being
created later, after the load had dropped.
The fix adds error handling to delete the erroneous
.ibd file. This error was less likely to
occur in MySQL 5.5 and 5.6, because raising the number of
InnoDB undo slots increased the number of
simultaneous transactions needed to trigger the bug, from 1K to
Improved the accuracy of persistent
statistics for large tables. The estimate of distinct records
could be inaccurate if the index tree was more than 3 levels
InnoDB: Shutdown could hang with messages like this in the log:
Waiting for purge thread to be suspended
After 1 hour, the shutdown times out and
mysqld quits. This problem is most likely to
occur with a high value for
(Bug #11765863, Bug #58868, Bug #60939)
DROP TABLE failed due to all
undo slots being in use, the error returned was
Unknown table '...' rather than the
expected Too many active concurrent
(Bug #11764724, Bug #57586)
References: See also Bug #11764668, Bug #57529.
Server startup could produce an error for temporary tables using
InnoDB storage engine, if the path in the
$TMPDIR variable ended with a
/ character. The error log would look like:
120202 19:21:26 InnoDB: Operating system error number 2 in a file operation. InnoDB: The error means the system cannot find the path specified. InnoDB: If you are installing InnoDB, remember that you must create InnoDB: directories yourself, InnoDB does not create them. 120202 19:21:26 InnoDB: Error: trying to open a table, but could not InnoDB: open the tablespace file './t/#sql7750_1_0.ibd'! InnoDB: Have you moved InnoDB .ibd files around without using the InnoDB: commands DISCARD TABLESPACE and IMPORT TABLESPACE? InnoDB: It is also possible that this is a temporary table #sql..., InnoDB: and MySQL removed the .ibd file for this.
The workaround for the problem was to create a similar temporary
table again, copy its
.frm file to
tmpdir under the name mentioned in the error
message (for example,
set to its normal value without a trailing slash, for example
/var/tmp. On startup, MySQL would see the
.frm file and issue
TABLE for the orphaned temporary table.
(Bug #11754376, Bug #45976)
When creating a view from a
SELECT statement that used
explicit partition selection, the partition selection portion of
the query was ignored.
Adding a partition to an already existing
LIST-partitioned table did not work correctly
if the number of items in the new partition was greater than 16.
This could happen when trying to add a partition using an
TABLE ... ADD PARTITION statement, or an
TABLE ... REORGANIZE PARTITION statement.
Partitioning: A function internal to the code for finding matching subpartitions represented an unsigned number as signed, with the result that matching subpartitions were sometimes missed in results of queries. (Bug #12725206, Bug #61765)
References: See also Bug #20257.
Executing mysqlbinlog with the
N was equal either to 0
or to a value greater than the length of the dump file, caused
it to crash.
This issue was introduced in MySQL 5.5.18 by the fix for Bug #32228 and Bug #11747416. (Bug #13593869, Bug #64035)
When starting the server, replication repositories were checked
even when the
equal to 0 (the default), in spite of the fact that a valid
nonzero value for
--server-id must be supplied
for a server that acts as either a master or a slave in MySQL
This could cause problems when trying to perform a live upgrade
from MySQL 5.5, although it was possible to work around the
issue by starting the server with
--skip-slave-start (in addition
to any other required options).
To avoid this problem, replication repositories are now checked
only when the server is started with
--server-id using a nonzero value.
(Bug #13427444, Bug #13504821)
Formerly, the default value shown for the
Port column in the output of
SHOW SLAVE HOSTS was 3306 whether
the port had been set incorrectly or not set at all. Now, when
the slave port is not set, the actual port used by the slave is
shown. This change also affects the default shown for the
--report-port server option.
Replication: A race condition could occur when running multiple instances of mysqld on a single machine, when more than slave thread was started at the same time, and each such thread tried to use the same temporary file concurrently. (Bug #12844302, Bug #62055)
It was possible on replication slaves where
FEDERATED tables were in use to get
timeouts on long-running operations, such as Error 1160
Got an error writing communication
FEDERATED tables did
not need to be replicated for the issue to occur.
(Bug #11758931, Bug #51196)
References: See also Bug #12896628, Bug #61790.
Statements that wrote to tables with
AUTO_INCREMENT columns based on an unordered
SELECT from another table could lead to the
master and the slave going out of sync, as the order in which
the rows are retrieved from the table may differ between them.
Such statements include any
TABLE ... SELECT statement. Such statements are now
marked as unsafe for statement-based replication, which causes
the execution of one to throw a warning, and forces the
statement to be logged using the row-based format if the logging
(Bug #11758263, Bug #50440)
On Windows replication slave hosts,
SLAVE took an excessive length of time to complete
when the master was down.
(Bug #11752315, Bug #43460)
from the binary log in its output, even if database
dbname was never referenced in the
binary log. This was due to the fact that
COMMIT statements were not
associated with any database in the binary log. Now in such
cases, the current database is tracked so that only those
SET INSERT_ID assignments that are made in
the context of changes to tables in database
dbname are actually printed in the
(Bug #11746146, Bug #23894)
References: See also Bug #23890, Bug #46998, Bug #11761686, Bug #54201, Bug #11754117, Bug #45670.
mysqldump tried to execute
SET OPTION, which failed when
used against 5.6 or higher servers because the deprecated
OPTION keyword has been removed from
The optimizer did not perform constant propagation for views, so a query containing views resulted in a less efficient execution plan than the corresponding query using only base tables. (Bug #13783777)
A memory leak could occur for queries containing a subquery that
GROUP BY on an outer column.
After using an
statement to change the
property for an
InnoDB table, for example
when switching from an uncompressed to a compressed table,
subsequent server restarts could fail with a message like:
InnoDB: Error: data file
path/ibdata2 uses page size 1024, InnoDB: but the only supported page size in this release is=16384
This issue is a regression introduced in MySQL 5.5.20. (Bug #13698765, Bug #64160)
In debug builds, a Debug Sync timeout warning was treated as an error, causing an assertion to be raised. (Bug #13688248)
_mi_print_key() iterated one time too many
when there was a
NULL bit, resulting in
Pushing down to
InnoDB an index
condition that called a stored function resulted in a server
crash. This kind of condition is no longer pushed down.
SELECT from a subquery that
returned an empty result could itself fail to return an empty
result as expected.
(Bug #13651009, Bug #13650418)
For debug builds, negative values with a zero integer part and nonzero fractional part (such as -0.1111) were not detected, so the negative fractional part was later cast to a large unsigned number and raised an assertion. (Bug #13616434)
If during server startup a signal such as
SIGHUP was caught prior to full server
initialization, the server could crash. This was due to a race
condition between the signal handler thread and the main thread
performing server initialization. To prevent this from
happening, signal processing is now suspended until full
initialization of all server components has been completed
(Bug #13608371, Bug #62311)
The shared version of
libmysqlclient did not
export these functions for linking by client programs:
An aggregated expression of type
MAX() should return
but could instead return the empty set if the query was
implicitly grouped and there was no
clause that evaluates to
Left join queries could be incorrectly converted to inner joins and return erroneous result sets. (Bug #13595212)
Date-handling code could raise an assertion attempting to calculate the number of seconds since the epoch. (Bug #13545236)
For queries that used a join type of
ref_or_null, the optimizer
could skip the filesort operation and sort the results
For some queries, a filesort operation was done even when the result contained only a single row and needed no sorting. (Bug #13529048)
The optimizer could return an incorrect select limit in some
cases when a query included no explicit
In some cases, the optimizer failed to use a covering index when that was possible and read data rows instead. (Bug #13514959)
References: This bug was introduced by Bug #11746275.
The Performance Schema instrumentation for stages did not fully
ENABLED column in the
Converting a string ending with a decimal point (such as
'1.') to a floating-point number raised a
data truncation warning.
Use of an uninitialized
could cause a server crash.
Some outer joins that used views as inner tables did not evaluate conditions correctly. (Bug #13464334)
A query that used an index on a
CHAR column referenced in a
BETWEEN clause could return invalid results.
(Bug #13463488, Bug #63437)
Expressions that compared a
BIGINT column with any
non-integer constant were performed using integers rather than
decimal or float values, with the result that the constant could
be truncated. This could lead to any such comparison that used
BETWEEN yielding false positive or
(Bug #13463415, Bug #11758543, Bug #63502, Bug #50756)
An application linked against
crash in debug mode with a
detected error if it tried to connect without
specifying the user name.
Instantiating a derived table for a query with an empty result caused a server crash. (Bug #13457552)
When the optimizer performed conversion of
DECIMAL values while evaluating
range conditions, it could produce incorrect results.
On Windows, rebuilds in a source distribution failed to create the initial database due to insufficient cleanup from the previous run or failure to find the proper server executable. (Bug #13431251)
Implicitly grouped queries with a
and no matching rows could return incorrect results.
For debug builds, enabling
optimizer_trace could cause an
assertion to be raised.
Enabling index condition pushdown could cause performance degradation. (Bug #13430436)
When a fixed-width row was inserted into a
MyISAM temporary table, the entire
content of the record buffer was written to the table, including
any trailing space contained in
VARCHAR columns, the issue being
that this trailing space could be uninitialized. This problem
has been resolved by insuring that only the bytes actually used
to store the
VARCHAR (and none extra) are
copied and inserted in such cases.
Fractional seconds parts were lost for certain
When merging ranges that effectively resulted in a full index scan, the optimizer did not discard the range predicate as unneeded. (Bug #13354910)
MyISAM tables (unlike
MyISAM tables) did not use the dynamic
row format when they contained
VARCHAR columns, resulting in
larger temporary files (and more file I/O) than necessary.
EXPLAIN, it was
assumed that only the default multi-range read implementation
could produce an ordered result; this meant that when a query on
a table that used a storage engine providing its own sorted MRR,
it was ignored, so that
EXPLAIN failed to
Using MRR even when a multi-range read
Some multiple-table updates could update a row twice. (Bug #13095459)
idle event timings were
not normalized to the same units as wait timings.
In MySQL 5.6.3, a number of status variables were changed to
longlong types so that they would roll over
much later. However, the format string used by
mysqladmin status to print
per second values did not reflect this, causing such
values to be misreported.
References: See also Bug #42698. This bug was introduced by Bug #11751727.
For debug builds, two assertions could be raised erroneously for
When the result of a stored function returning a non-integer
type was evaluated for
NULL, an incorrect
type warning (Warning 1292 Truncated incorrect
INTEGER value) is generated, although such a test
for NULL should work with any type. This
could cause stored routines not handling the warning correctly
The issue could be worked around by wrapping the result in an
expression, using a function such as
(Bug #12872824, Bug #62125)
When running mysqldump with both the
--flush-logs options, the
flushing of the log performed an implicit
Statements That Cause an Implicit Commit), causing more than one
transaction to be used and thus breaking consistency.
(Bug #12809202, Bug #61854)
mode enabled, columns that were not aggregated in the select
list or named in a
GROUP BY were incorrectly
NO_BACKSLASH_ESCAPES SQL mode
within stored procedures on slave servers could cause
Passing a user variable as an argument to
GROUP_CONCAT() could cause a
server exit if the variable value changed during query
LOAD INDEX INTO
CACHE could cause a server exit if the index cache was
ONLY_FULL_GROUP_BY SQL mode enabled, a
query that uses
GROUP BY on a column derived
from a subquery in the
FROM clause failed
column isn't in GROUP BY error, if the
query was in a view.
Attempting to execute
on a temporary
MERGE table having
an underlying temporary table rendered the
MERGE table unusable, unless the
ALTER TABLE specified a new list of
(Bug #11764786, Bug #57657)
It was possible in the event of successive failures for mysqld_safe to restart quickly enough to consume excessive amounts of CPU. Now, on systems that support the sleep and date system utilities, mysqld_safe checks to see whether it has restarted more than 5 times in the current second, and if so, waits 1 second before attempting another restart. (Bug #11761530, Bug #54035)
References: See also Bug #11758970, Bug #51242, Bug #11759718, Bug #52051.
If an attempt to initiate a statement failed, the issue could not be reported to the client because it was not prepared to receive any error messages prior to the execution of any statement. Since the user could not execute any queries, they were simply disconnected without providing a clear error.
After the fix for this issue, the client is prepared for an error as soon as it attempts to initiate a statement, so that the error can be reported prior to disconnecting the user. (Bug #11755281, Bug #47032)
.OLD files were not included
among the files deleted by
DATABASE. Files with this extension are now also
deleted by the statement.
(Bug #11751736, Bug #42708)
A prepared statement using a view whose definition changed between preparation and execution continued to use the old definition, which could cause the prepared statement to return incorrect results. (Bug #11748352, Bug #36002)
Some debugging information was written to the buffer after a flush, resulting in the information not appearing until the next flush. (Bug #64048, Bug #13608112)
Locale information for
function instances was lost in view definitions.
(Bug #63020, Bug #13344643)
mysqlhotcopy failed for databases containing views. (Bug #62472, Bug #13006947, Bug #12992993)
The VIO description string was initialized even for connections where it was unneeded. (Bug #62285, Bug #12951586)
On Windows, pasting multiple-line input including a CRLF terminator on the last line into the mysql client resulted in the first character of the last line being changed, resulting in erroneous statements. Handling of newlines in pasted input was also incorrect. (Bug #60901, Bug #12589167, Bug #64104, Bug #13639107)
The contents of the
shared-compat RPM packages had been changed
in versions 5.5.6 and 5.6.1 to avoid the overlap which they
traditionally had (and still have in MySQL 5.0 and 5.1).
However, the RPM meta information had not been changed in
accordance, and so RPM still assumed a conflict between
RPM packages. This has been fixed.
(Bug #60855, Bug #12368215)
References: See also Bug #56150.
UPDATE IGNORE returned an incorrect count for
number of rows updated when there were duplicate-key conflicts
in a multiple-table update.
(Bug #59715, Bug #11766576)
The optimizer mishandled
with nested joins; for example, by not evaluating tables in the
(Bug #59487, Bug #11766384, Bug #43368, Bug #11752239, Bug #60080, Bug #11766858)
A subquery involved in a comparison requiring a character set conversion caused an error that resulted in a server crash. (Bug #59185, Bug #11766143)
The embedded server crashed when
argc = 0.
(Bug #57931, Bug #12561297)
If tables were locked by
LOCK TABLES ...
READ in another session,
SET GLOBAL read_only
= 1 failed to complete.
(Bug #57612, Bug #11764747)
Invalid memory reads could occur when
cmp_item_sort_string::store_value() tried to
refer to a temporary value that could be changed or deleted by
(Bug #57510, Bug #11764651)
Assigning the result of a subquery to a user variable raised an
assertion when the outer query included
(Bug #57196, Bug #11764371)
For comparisons containing out-of-range constants, the optimizer permitted warnings to leak through to the client, even though it accounted for the range issue internally. (Bug #56962, Bug #11764155)
CREATE TABLE error
message was improved.
(Bug #54963, Bug #11762377)
handle_segfault() signal-handler code in
mysqld could itself crash due to calling
(Bug #54082, Bug #11761576)
Using myisamchk with the sort recover method to repair a table having fixed-width row format could cause the row pointer size to be reduced, effectively resulting in a smaller maximum data file size. (Bug #48848, Bug #11756869)
cause the server to crash.
(Bug #48726, Bug #11756764)
not be set larger than 4GB on 64-bit systems.
(Bug #45702, Bug #11754145)
The stored routine cache was subject to a small memory leak that over time or with many routines being used could result in out-of-memory errors.
The fix for this issue also introduces a new global server
stored_program_cache which can
be used for controlling the size of the stored routine cache.
(Bug #44585, Bug #11753187)
Under some circumstances, the result of
depended on the contents of the previous row.
(Bug #42404, Bug #11751514)
Setting an event to
DISABLED status and with
ON COMPLETION NOT PRESERVE attribute
caused it to be dropped at the next server restart.
(Bug #37666, Bug #11748899)
Due to improper locking, concurrent inserts into an
ARCHIVE table at the same time as
repair and check operations on the table resulted in table
(Bug #37280, Bug #11748748)
Stored functions could produce an error message that referred to
ORDER BY even though the offending statement
within the function had no such clause.
(Bug #35410, Bug #11748187)
The decision about how to sort a result set could be reported
EXPLAIN for some statements,
Using filesort or
temporary to be reported when they should not have
been or vice versa. This could occur for statements that
included index hints, that had the form
SQL_BIG_RESULT ... GROUP BY, that used
LIMIT, or that used
ORDER BY, and